1. Field of the Invention
The present invention relates to a method of correcting bonding coordinates, and more particularly, to a method of correcting bonding coordinates according to the locations of a die and leads that are loaded in a wire bonder apparatus for bonding.
2. Description of the Related Art
FIG. 1 illustrates a die 201 and leads 203 (e.g., of a lead frame) that are loaded in a wire bonder apparatus for bonding. Referring to FIG. 1, reference numeral 202 indicates a bond pad of a plurality of bond pads labeled P1 through PN, label P-1 indicates a first die recognition area, label P-2 indicates a second die recognition area, label L-1 indicates a first lead recognition area, and label L-2 indicates a second lead recognition area.
FIG. 2 is a flowchart of a conventional teaching algorithm that is used for a conventional method of correcting bonding coordinates. Referring to FIGS. 1 and 2, before continuous bonding is performed, an operator performs a teaching operation (i.e., manually identifying visual points and data entry) to assign coordinates to bonding points of the bond pads P1 through PN of the reference die 201, bonding points of the leads 203, and recognition areas P-1, P-2, L-1, and L-2. The recognition areas can be generally called eye points.
When the operator completes the teaching operation (Operation S201), a controller (not shown) of a wire bonder apparatus stores the bonding coordinates of the bond pads and leads (Operation S202). Also, the controller of the wire bonder apparatus stores center coordinates and reference image data of the recognition areas (Operation S203).
FIG. 3 is a flowchart of a conventional method of correcting bonding coordinates when materials and elements are loaded in a wire bonder apparatus for bonding. Referring to FIGS. 1 through 3, the controller of the wire bonder apparatus searches for locations of the die recognition areas P-1 and P-2 and the lead recognition areas L-1 and L-2 with respect to the die 201 and the leads 203 (Operation S301). In detail, a vision system (not shown) compares image data with the reference image data (i.e., image data of a previous or example die and leads) to search for the locations of the die recognition areas P-1 and P-2 and the lead recognition areas L-1 and L-2 of the instant die that is loaded for bonding.
If the locations of the die recognition areas P-1 and P-2 and the lead recognition areas L-1 and L-2 are successfully searched for, the controller of the wire bonder apparatus compares the locations of the recognition areas P-1, P-2, L-1, and L-2 of the instant die and leads with set locations, and corrects the bonding coordinates of the instant die 201 and the leads 203 according to the comparison result (Operations S302, S304, and S305).
If the search for the locations of the instant die recognition areas P-1 and P-2 or the location of the instant lead recognition areas L-1 and L-2 fails, the controller of the wire bonder apparatus indicates an arrangement error and discontinues the wire bonding (Operations S302 and S303).
In this conventional method of correcting bonding coordinates, the search for the locations of the instant die recognition areas P-1 and P-2 in Operation S302 frequently fails, because dies in a lot may vary unpredictably and non-uniformly. For example, the die recognition areas P-1 and P-2 are frequently obscured by epoxy or tape that is applied during a die attach process before the wire bonding. Further, when a die is partially coated, the die recognition areas P-1 and P-2 may be coated.
Therefore, according to the conventional method of correcting bonding coordinates, since the search for the locations of the die recognition areas P-1 and P-2 fails frequently, the wire bonding is frequently discontinued. A method of correcting bonding coordinates that failed less frequently would, therefore, be an important improvement in the art.